The present invention relates to the field of communications and more particularly to radio communications.
In conventional radio telephone communications systems, control, voice, and data information from a mobile switching center is received at a radio base station via a carrier protocol such as a T1, E1, or J1carrier protocol. Each carrier protocol can support a fixed number of channels or timeslots within a frame for communicating control, voice, and data information between the mobile switching center and a radio base station over a carrier bus. For example, the T1 carrier protocol can support 24 channels or timeslots per frame. Within a radio base station, the control, voice, and data information from the mobile switching center is received at a control board interface, and portions of this data can be communicated with other base station control boards and/or other base station devices over a radio base station bus using a bus interface of the same type as that used for the carrier from the mobile switching center. Thus, for example, a radio base station bus corresponding to the T1 carrier protocol discussed above would support 24 timeslots per frame.
Typically, the mobile switching center communicates control information to the radio base station over a control signaling link (CSL) (64 kb/s PCM timeslots). Conventional systems typically use a control radio interface (CRI) that supports a single CSL for all control information communicated between the mobile switching center and the radio base station. A single CSL occupies one timeslot per frame on the carrier bus or, in other words, 1/24 timeslots per frame is dedicated to control information. Control information is typically passed between base station control boards over the radio base station bus. A conventional CRI dedicates one timeslot per frame on the radio base station bus to control information.
More recently, a new control radio interface, CRI2, has been developed which allows up to four timeslots per frame on the carrier bus to be dedicated to control information. CRI2 supports a fixed number of five dedicated control timeslots per frame on the radio base station bus. Accordingly, bandwidth on the radio base station bus may be wasted.